Filtration method and device useable for removal of leukocytes and other blood components

ABSTRACT

The filtration method involves processing biological liquid from an enclosed flexible supply bag to a filtration media within a processing system wherein the flow of biological liquid within the system is restricted to allow the biological liquid to back up above the level of a port located upstream within the system and preventing gas from entering into the processing system through the port by maintaining the level of biological liquid above the port until the flow of biological liquid from the flexible supply bag ceases. The system automatically allows gas to enter into the system through the port when the flow of biological liquid ceases thereby draining the biological liquid into a receiving bag. The flow may be restricted by a narrow cross-sectional area within the processing system and the port may be covered by a hydrophobic filter media.

This application is a continuation of application Ser. No. 08/661,804filed Jun. 11, 1996 which application is now abandoned, which is acontinuation of application Ser. No. 08/449,362 filed May 24, 1995; nowabandoned, which is a division of application Ser. No. 08/209,523 filedMar. 10, 1994, now U.S. Pat. No. 5,472,605.

FIELD OF THE INVENTION

This invention relates generally to gravity feed liquid filtrationdevices. More particularly, this invention relates to a gravity feedliquid filtration device useable to filter blood and blood components.

BACKGROUND OF THE INVENTION

At the present time there are several disposable gravity feed bloodfiltration devices. All of these devices, however, require usermanipulation of vent filters during the filtration process. Themanipulation of the vent filters must take place at the proper timeduring the filtration process or the system will not filter properly andthe blood being filtered may be rendered unusable. Since, usermanipulation of vent filters is time consuming and costly, it isdesirable to achieve a liquid filtration device which may filter bloodwithout the manipulation of vent filters.

SUMMARY OF THE INVENTION

The shortcomings of the prior art may be alleviated using a filtrationmethod and apparatus in accordance with the principles of the presentinvention. The method involves processing biological liquid from anenclosed flexible supply bag to a filtration media with a processingsystem by restricting the flow of biological liquid within the system toallow the biological liquid to back up above the level of a port locatedupstream within the system, preventing gas from entering into theprocessing system through the port by maintaining the level ofbiological liquid above the port, until the flow of biological liquidfrom the flexible supply bag ceases, and automatically allowing gas toenter into the system through the port when the flow of biologicalliquid ceases thereby draining the biological liquid from the system.

The flow may be restricted by a narrow cross-sectional area within theprocessing system and the port may be covered by a hydrophobic filtermedia. The biological liquid may comprise blood or a blood product. Thefiltration media may comprise a leukocyte filter media and thebiological liquid may flow into a receiving bag. The receiving bag maybe located at a height below the leukocyte filter media and below theport. The port may be located at a height greater than the leukocytefilter media.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the detaileddescription of the preferred embodiments herein when read in conjunctionwith the drawings in which:

FIG. 1A depicts a sectional representation of an in line vent filteruseable in accordance with the principles of the present invention;

FIG. 1B depicts an isometric view of an in-line vent filter havingportions removed therefrom and useable in accordance with the principlesof the present invention;

FIG. 2 depicts a schematic sectional representation of a filtrationdevice constructed in accordance with the principles of the presentinvention;

FIG. 3 depicts a schematic representation of the filtration device andin-line vent filter used for filtering blood where a blood supply bag isfilled;

FIG. 4 depicts a schematic representation of the filtration device andin-line vent filter used for filtering blood where the blood supply bagis empty;

FIG. 5 depicts an outlet section of an embodiment of the filtrationdevice constructed in accordance with the principles of the presentinvention whereby a means for placing a first outlet in fluid flowrelationship with the second outlet of a second chamber of the device isintegrally formed with the outlet section of the device;

FIG. 6 depicts a sectional representation of the alternative embodimentof the filtration device having the outlet section depicted in FIG. 5;

FIG. 7 depicts an isometric view, having portions thereof removed, ofthe embodiment of the filtration device depicted in FIG. 6;

FIG. 8 depicts an isometric view of the inside surface of the firstsection of the embodiment of the filtration device depicted in FIG. 7;

FIG. 9 depicts the embodiment of the filtration device depicted in FIG.7 having the in-line vent filter, tubing, blood supply means and bloodcollecting means in an operational assembly;

FIG. 10 depicts a cross-sectional view of a lower section of theembodiment of the filtration device depicting one technique for sealinga plurality of filtration elements therein;

FIG. 11 depicts a cross-sectional view of the lower portion of anembodiment of the filtration device depicting an alternative techniquefor sealing a plurality of filtration elements;

FIG. 12 depicts a cross-sectional view of the lower portion of afiltration device constructed in accordance with the principles of thepresent invention depicting one technique for sealing the outer edges ofa plurality of filtration elements;

FIG. 13 depicts a cross-sectional view of the lower portion of afiltration device constructed in accordance with the principles of thepresent invention depicting an alternative technique for sealing theouter edges of a plurality of filtration elements; and

FIG. 14 depicts a schematic representation of yet another embodiment ofthe filtration device constructed in accordance with the principles ofthe present invention along with a vent filter blood supply means andblood collecting means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The liquid filtration device constructed in accordance with theprinciples of the present invention utilizes an air venting meansoperatively engaged to a fluid filtration means. One embodiment of thefiltration apparatus constructed in accordance with the principles ofthe present invention is shown in FIG. 2, and its operation depicted inFIGS. 3 and 4.

FIG. 1A depicts a schematic representation of an in line vent filter 15useable as an air venting means in accordance with the principles of thepresent invention. As described herein the automatic in-line vent filterautomatically vents the inlet of the fluid filtration system when fluidstops flowing from feed blood bag 20. When fluid flows from feed bloodbag 20 the in-line vent filter 15 automatically stops venting. This ventfilter may consist of an inlet section 1, an outlet section 2, and asterilizing grade hydrophobic filter 3. The hydrophobic filter preventsthe passage of liquid therethrough, (assuming the liquid is at apressure less than the bubble point pressure of the filter material)while allowing the passage of air therethrough. Air is capable ofpassing through the hydrophobic filter even after the filter has beenexposed to a liquid. The inlet section 1 may include vent ports 4 whichare in air flow relationship to the outside of the vent filter. Thehydrophobic filter 3 is sealed to the inlet section 1 by seals 5 and 6,which are preferably heat seals. However, any type of reliable leakproof seals which are well known in the art, such as ultrasonic, solventor adhesive type seals may be used in accordance with the invention. Thein-line vent filter 15 may be a round device and the hydrophobic filtermay be shaped as a disc with a hole punched in its center. However, thein-line vent filter 15 is not limited to any particular shape and mayinclude more than one hydrophobic filter 3. Seal 5 should extend aroundthe entire periphery of the center hole of the hydrophobic filter 3 andhence around the entire periphery of a port 7 sealing the hydrophobicfilter 3 to the inlet section 1. Seal 6 seals the hydrophobic filter tothe inlet section 1 around the entire outer periphery of the hydrophobicfilter 3. Although liquid within the chamber 10 may not pass through thehydrophobic filter 3, air may enter vent ports 4 and pass throughhydrophobic filter 3. The inlet section 1 of the vent filter may alsoinclude a tubing socket 8 into which a length of tubing 14 may beinserted. The tubing socket 8 is in fluid flow relationship with theport 7 which should be approximately the same diameter as the insidediameter of tubing 14.

The outlet section 2 may be bonded to the inlet section 1 by a seal 9.Seal 9 should extend around the entire periphery of the vent filter 15thus forming chamber 10. Seal 9 is preferably an ultrasonic seal.However, other seals including heat seals, adhesive seals or any otherhermetic seal may be used. Outlet section 2 includes restriction 11forming an outlet of chamber 10, and tubing socket 12 extending from therestriction 11 into which a length of tubing 13 may be insertedRestriction 11 is typically a long small diameter port which connectschamber 10 to tubing 13. The cross sectioned area of the restrictionshould be less than the cross sectioned area of the inlet to allow fluidflowing therethrough to fill chamber 10 and contact hydrophobic filter3.

Liquid to be filtered enters the vent filter 15 via tubing 14 and port 7and exits via restriction 11 and tubing 13. The length and diameter ofrestriction 11 depends upon viscosity of the liquid being filtered andshould be sized so that liquid entering the in-line vent filter 15through port 7 will back up and fill chamber 10. At this condition, theliquid in chamber 10 will be at a pressure head greater than atmosphericpressure and below the bubble point pressure of the hydrophobic filter3. Since a hydrophobic filter can not pass an aqueous solution at apressure below the bubble point of the hydrophobic filter, fluid willnot exit through ports 4. Likewise since the pressure head in chamber 10is greater than atmospheric pressure air can not enter chamber 10 viaports 4. The restriction 11 should not restrict the flow of fluidthrough the liquid filtration device 129 (described below) which may beattached to the opposite end of the tubing 13. When fluid flow into port7 of the vent filter 15 ceases the pressure head in chamber 10 shalldecrease to zero enabling air to enter chamber 10 via ports 4 andhydrophobic filter 3 thus draining restriction 11 and tubing 13.

FIG. 1B depicts an in-line vent filter which is similar in structure andoperation to the vent filter depicted in FIG. 1A but also contains aninside channel 17 and a plurality of support ribs 18.

As depicted in FIG. 1B the inside portion of inlet section 1 of the ventfilter 15 may contain channel 17 which provides a gap between thehydrophobic filter 3 and inlet section 1 which leads to vent ports 4.The outlet half 2 contains a plurality of support ribs 18 which assistin supporting the hydrophobic filter 3.

FIG. 2 is a schematic representation of the filtration device 129 whichis suited for blood filtration and leukocyte and/or other bloodcomponent removal therefrom. Filtration device 129 includes inletsection or half 101 which is bonded to an outlet section or half 102 bya seal 120. This seal 120 is preferably an ultrasonic seal. However,other seals such as heat seals or adhesive seals or any other hermeticseal may be used. Inlet section 101 includes tubing socket 113 intowhich the outlet end of tubing 13 is affixed as well as port 122. Theinlet end of tubing 13 is affixed to the outlet of the vent filter 15.Inlet section 101 contains side walls 131 extending about the peripheryof bottom wall 130. Side walls 131 and bottom wall 130 define chamber108. Any fluid exiting the vent filter 15 via tubing 13 will enterchamber 108 through port 122.

Outlet section 102 of the filtration device 129 may include a tube 110affixed thereto which defines a passage 111. Tube 110 is preferablyround and multi-diameter, however, other shapes may suffice. Outletsection 102 may also include a port 121, port 123, port 124, tubingsocket 114 and tubing socket 115. Outlet section 102 includes a bottomwall 132 and side walls 133 extending about the periphery thereof. Sidewalls 133 and bottom wall 132 define chamber 109 of outlet half 102. Acover 112 may be affixed to outlet half 102 by seal 125. Seal 125 ispreferably an ultrasonic seal. However, other seals may suffice. Thecover 112 and multi diameter tube 110 define a chamber 111 which is influid flow relationship with chamber 109 via port 121. A hydrophobicfilter 104 is sealed to an end of multi diameter tube 110, extendinginto chamber 108, by peripheral seal 105. Peripheral seal 105 ispreferably a heat seal. Again, however, other types of reliable leakproof seals such as ultrasonic or adhesive seals may suffice. Ahydrophilic filter 106 may be sealed to outlet section 102 by peripheralseal 107 to cover port 123. When dry, the hydrophilic filter 106 allowsthe passage of air therethrough except at peripheral seal 107, whichshould preferably be a heat seal. However, other types of reliable leakproof seals such as ultrasonic or adhesive seals may suffice. When wet,the hydrophilic filter 106 does not allow the passage of airtherethrough unless the air pressure is above the bubble point pressureof the hydrophilic filter 106.

The hydrophobic filter 104 covers the end of tube 110 and, therefore,should be the same shape as the end of tube 110. Filtering elements 103,which may be leukocyte removing elements for blood filtration, should beshaped to divide the filtration device 129 into chamber 108 and chamber109. The filtration elements 103 defines, along with inlet section 101,chamber 108 and, along with outlet section 102, chamber 109. Eachfiltration element 103 may have a hole therein which is positioned toenable the hole to align with tube 110 when the filtration elements 103are placed into the filtration device 129. Therefore, it is preferredthat the hole have the same shape and size of the small end of tube 110.The filtration elements 103 fit into and are contained by a filterelement receptacle which is defined by side walls 145 of outlet section102, and by shelf 147 of outlet section 102 and sealing rib 148 of inletsection 101.

The filtration device 129 in FIG. 2 contains four (4) filtrationelements 103. When using the filtration device 129 for blood filtration,the filtration elements 103 may include leukocyte removing elementswhich are known in the art. Depending on the application, the filtrationdevice 129 could be manufactured to accept more or less than fourfiltration elements 103. The outside periphery of the filtrationelements 103 may be sealed to the filtration device 129 by a pinch seal119 wherein the outside periphery of the filtration elements 103 ispressed between sealing rib 148 of inlet section 101 and shelf 147 ofoutlet section 102 creating a seal. Likewise the filtration elements 103may be sealed to the tube 110 by a pinch seal 126. In this case, awasher 118 which may be press fitted about multi diameter tube 110forces the filtration elements 103 between washer 118 and the lip 99 oftube 110 to form seal 126. Alternatively washer 118 could beultrasonically welded, heat sealed or sealed with an adhesive to tube110. Also, filtration elements 103 could be sealed to the filtrationmeans 129 and multi diameter tube 110 by other reliable sealingtechniques.

A first outlet from the chamber 109 is formed by port 124 which is influid flow relationship with Tee 127 via siphon tube 116. A secondoutlet from chamber 109 is formed by port 123 which is in fluid flowrelationship with Tee 127 via tube 128. Tee 127 is in fluid flowrelationship with a fluid or liquid receiving means via tubing 117. Thetube 128, tee 127 and tube 116 function as a means for placing the firstoutlet formed by port 124 in fluid flow relationship with the secondoutlet formed by port 123. The receiving means could be a blood bag oreven an open container. However, when using the system for bloodfiltration, a sterile receiving blood bag should be used.

Although FIG. 2 illustrates the inlet port 122 near the top of inlethalf 101, port 122 may be placed in other locations. Moreover, port 122need not be located on the vertical center line of inlet half 101.However, port 122 should not be placed adjacent to or directly belowhydrophobic filter 104, particularly if the gap between wall 130 ofinlet half 101 and hydrophobic filter 104 is small.

FIG. 3 illustrates one embodiment of the apparatus or system inaccordance with the present intention including the vent filter 15, thefiltration means 129, a feed blood bag 20, a receiving blood bag 21, andall the necessary interconnecting tubing. Typically, the user wouldpurchase the system without feed blood bag 20. The user would receivethe system sterilized with the inlet end of tubing 14 sealed to maintainsystem sterility. Therefore, with the exception of ports 4 the system isclosed. Moreover, the hydrophobic filter 3 of vent filter 15 should be asterilizing grade filter which is sealed with a leak tight seal to theinlet section 1 of the vent filter 15. Therefore, the inside of thesystem should remain sterile.

When filtering blood the user would first close tubing 13 (near theoutlet side of vent filter 15) with a tubing clamp (not illustrated) andthen make a sterile connection between the inlet end of tubing 14 andthe feed blood bag 20 using a sterile docking device known in the art.The actual sterile connection is made between tubing 14 and a shortlength of tubing which is a part of feed blood bag 20. The resultingsystem is illustrated in FIG. 3. Feed blood bag 20 may be suspended froman appropriate mechanism. The filtration means 129 may also be suspendedfrom the mechanism or by tubing 13. A receiving blood bag 21 may besuspended by the mechanism or may rest on a surface such as a bench topor the like. Once the sterile connection is made between feed blood bag20 and tubing 14 and the system components are suspended, blood willflow from feed blood bag 20 and fill tubing 14, vent filter 15, and theupper part of tubing 13 to the point where a tubing clamp (not shown)clamps tubing 13. The air that was in tubing 14, vent filter 15 and theupper part of tubing 13 will vent through a sterilizing gradehydrophobic filter 3 and then through ports 4 to the atmosphere. Some ofthis air may also bubble to the top of feed blood bag 20.

Referring still to FIG. 3, once the tubing clamp (not shown) is openedblood will begin to flow from feed blood bag 20, through tubing 14,through vent filter 15, tubing 13 and finally through port 122 intochamber 108. In FIG. 3, the blood flow is indicated by the solid arrows.As blood begins to fill chamber 108 from the bottom up, air will ventfrom chamber 108 through the unwetted portions of filtration elements103 (i.e. through the portion of the filtration elements 103 above theblood level) and through hydrophobic filter 104. The air that ventsthrough hydrophobic filter 104 will pass through chamber 111 and thenthrough port 121 and finally into chamber 109. The air that ventsthrough the unwetted portions of filtration pads 103 will pass directlyinto chamber 109. All of the air that vents from chamber 108 to chamber109 will then vent from chamber 109 through port 124 and then throughsiphon tube 116 into tee 127; and from chamber 109 through hydrophilicfilter 106 and then through port 123 and then through tube 128 into Tee127. The air will then vent from Tee 127 through tube 117 into receivingblood bag 21.

Once the blood level in chamber 108 is high enough to cover hydrophobicfilter 104 air will stop venting from chamber 108 through hydrophobicfilter 104 and all venting of chamber 108 will occur through theunwetted portions of filtration elements 103 (which in this bloodfiltration application may include leukocyte removing elements orelements used to remove other blood components). Chamber 108 willcontinue to fill with blood until all of the air in chamber 108 has beenvented and chamber 108 is full of blood.

After the layers of the filtration elements 103 become wet, leukocytedepleted blood will start to pass from the elements 103 into chamber109. This leukocyte depleted blood flow into chamber 109 will begin ator near the bottom of chamber 109. Because the surface area of theelements 103 is much greater than the surface area of the hydrophilicfilter 106, and because the initial flow rate of blood through theelements 103 is high, and because the bubble point pressure of thehydrophilic filter 106 must be greater than pressure head at hydrophilicfilter 106 relative to receiving blood bag 21, the following sequence ofevents will occur. Once the blood level in chamber 109 fills to thelevel where port 124 is covered the air pressure in chamber 109 willstart to increase because the flow rate of leukocyte depleted bloodentering chamber 109 will be greater than the flow rate of air exitingchamber 109 through hydrophilic filter 106 (because of the necessarymaximum pore size of hydrophilic filter 106). This increase in airpressure in chamber 109 will cause blood to flow out of port 124 andinto siphon tube 116. The blood level in tube 116 will then rise fasterthan the blood level in chamber 109. The leukocyte depleted blood intube 116 will reach Tee 127 and fill Tee 127, the hydrophilic filter 106will not be wet by the leukocyte depleted blood on the Tee side ofhydrophilic filter 106 if tube 128 is of sufficient length or port 123is sufficiently small. Assuming that one or both of these conditions istrue the leukocyte depleted blood in Tee 127 will exit Tee 127 and thenflow down tubing 117 into the receiving blood bag 21. At this point thepressure head at the bottom of chamber 108 relative to the top of thesupply bag 20 will be greater than, the relative pressure head at thetop of chamber 108. However, the pressure of the air in chamber 109 willbe above atmospheric pressure and the pressure head in Tee 127 relativeto the receiving blood bag 21 will be less than the pressure head at thetop of chamber 109 and at the bottom of chamber 109. Hence the pressurein Tee 127 will be lower than the pressure in chamber 109. Therefore airwill be sucked from chamber 109 through hydrophilic filter 106, thenthrough port 123, then through tube 128 into Tee 127. At this pointthere will be a mixed stream of leukocyte depleted blood and air flowingdown tubing 117 into receiving blood bag 21. As air is evacuated fromchamber 109 the leukocyte depleted blood level in chamber 109 will rise.This process will continue until the level of leukocyte depleted bloodin chamber 109 either covers hydrophilic filter 106 or until hydrophilicfilter 106 becomes wetted by capillary action. Once the hydrophilicfilter 106 is wet it will no longer allow air passage therethroughunless the air pressure exceeds the bubble point pressure of thehydrophilic filter 106. The pore size of hydrophilic filter 106 shouldbe chosen so that once hydrophilic filter 106 is wet it will not allowair passage therethrough for the duration of the process. To assure thatthere will be a minimum amount of air trapped at the top, of chamber 109it is preferred that the volume of chamber 109 around hydrophilic filter106 be kept to a minimum.

As feed blood bag 20 continues to drain, tubing 14, vent filter 15,tubing 13 and chamber 108 will be full of unfiltered blood. Chamber 109,siphon tube 116, tee 127 and tubing 117 will be full of leukocytedepleted blood and receiving blood bag 21 will be partially filled withleukocyte depleted blood with a small air pocket at the top of receivingblood bag 21 due the air that was initially purged from the system. Thepressure head at the top of chamber 108 relative to the supply bag 20will still be less than the pressure head at the bottom of chamber 108relative to the supply bag 20. The pressure head at the bottom ofchamber 109 relative to the supply bag will be equal to the pressurehead at the bottom of chamber 108 less the pressure drop across theleukocyte removing pads 103 and the pressure head in Tee 127 relative tothe receiving bag will be slightly greater than previously when thereceiving bag began to fill due to the fact that receiving blood bag 21has begun to fill. Throughout the process the external pressure on feedblood bag 20 and receiving blood bag 21 will be atmospheric.

From the beginning of the filtration process when blood begins to drainfrom feed blood bag 20, the pressure in chamber 108 will always begreater than the pressure in chamber 109. Therefore, air will never flowfrom chamber 109 into chamber 108. Likewise leukocyte depleted bloodwill never flow from chamber 109 into chamber 111 as long as port 121 issufficiently small.

Referring to FIG. 4, when feed blood bag 20 has emptied tubing 14 willhave an air tight cap (i.e. collapsed feed blood bag 20) at its top. Thepressure head due to the blood in tubing 14 is now negated by thenegative pressure head due to the leak tight cap at the top of tubing 14and the pressure in chamber 10 of the vent filter 15 will beatmospheric. Air can now enter ports 4 of vent filter 15 and passthrough sterilizing grade hydrophobic filter 3 into chamber 10 of ventfilter 15. The air entering chamber 10 will displace the blood inchamber 10 causing chamber 10 to drain. Once chamber 10 has drained,restriction 11 will drain and then tubing 13 will drain. Since the inputpressure to the system (at ports 4) is atmospheric and the pressure headrelative to the receiving blood bag 21 in Tee 127 is less thanatmosphere, draining will continue and receiving blood bag 21 willcontinue to fill. At this time, port 122 is at atmospheric pressure andthe pressure head at the top of chamber 108 is less than atmospheric.Hence air will now enter chamber 108 through port 122 and bubble to thetop of chamber 108 thus draining chamber 108 from the top down. Sincethe pressure head in Tee 127 remains relatively lower than that inchamber 108, chamber 108 will continue to drain.

Once the blood level in chamber 108 drains to below the level ofhydrophobic filter 104 air will begin to flow from chamber 108 intochamber 111 and then through port 121 into chamber 109. Air will flowfrom chamber 108 to chamber 109 through the aforementioned path becausethe void part of chamber 108 is at atmospheric pressure and port 121 hasa lower pressure relative to the receiving blood bag 21. To ensure thatchamber 108 completely drains before air entering chamber 109 throughport 121 drains chamber 109 the following criteria should be used:

a) Hydrophobic filter 104 should be of the minimum surface areanecessary to allow drainage of chamber 109 in a reasonable time period.It should also be of the minimum surface area necessary so that aminimum amount of active surface area is removed from filtrationelements 103 to allow for tube 110.

b) Multi diameter tube 110 should be placed as close to the bottom ofchamber 108 as other design considerations permit.

c) For maximum safety hydrophobic filter 104 should be of sterilizinggrade.

When air starts to enter chamber 109 from port 121 the pressure head atport 121 is greater than the pressure head at the top of chamber 109.Hence air entering chamber 109 from port 121 will bubble up to the topof chamber 109 and displace leukocyte depleted blood in chamber 109 fromthe top down. Because hydrophilic filter 106 is now wet air can not flowfrom chamber 109 through hydrophilic filter 106, port 123 and tubing 128into Tee 127. Hence tubing 117 is not allowed to drain via hydrophilicfilter 106. If tubing 117 were allowed to drain via hydrophilic filter106 the filtered blood in chamber 109 would only drain to the bottomlevel of Tee 127. Chamber 109 will continue to drain in this manneruntil the leukocyte depleted blood level reaches the top of port 124.Then the tube 116 will be drained and tubing 117 will drain to theleukocyte depleted blood level at the top of receiving blood bag 21.Tubing 117 should then be sealed close to the receiving blood bag 21 andreceiving blood bag 21 along with the short length of sealed tubing 117may be cut from the rest of the system and is ready for use. The rest ofthe system (i.e. feed blood bag 20, vent filter 15, fluid filtrationmeans 129, Tee 127 and all remaining tubing should be discarded in aproper manner.

The air that initially fills the voids in the system is purged intoreceiving blood bag 21 when the system is primed with blood. To minimizethe amount of air that is purged into receiving blood bag 21 the voidvolume should be kept to a minimum. To minimize the void volume the gapbetween wall 130 of inlet section 101 and hydrophobic filter 104, shouldbe kept to a minimum. Therefore, port 122 of inlet section 101 shouldnot be placed adjacent to or directly below hydrophobic filter 104.

FIGS. 5-9 illustrates an alternative embodiment of the filtration device229 constructed in accordance with the principals of the presentinvention. This embodiment may be easily manufactured using disposableinjection molded plastic components. Moreover, the filtration device 229may be designed so that the user can easily hang all the systemcomponents from a hanging means such as a pole with hooks to allow forgravity feed of the fluids, such as blood, to be filtered. Thisembodiment operates in the same manner as the embodiment previouslydiscussed.

Referring to FIG. 5, in this embodiment the means for placing the firstoutlet, formed by port 124 of chamber 109, in fluid flow relationshipwith the second outlet, formed by port 123 of chamber 109, is integrallyformed to outlet section 202. A conduit 251 is formed by a ridge 249extending from the outlet section 202 and an outlet cover 212 which issealed to the ridge 249. Ridge 249 and outlet cover 212 are sealed toprevent fluid flowing within conduit 251 from leaking therefrom. Aninterior ridge 250 extends from the outlet section 202 but withinconduit 251. Raised ridge 250 also contacts outlet cover 212 to form achamber ill which is isolated from conduit 251 so that fluid withinconduit 251 cannot enter chamber 111. Within chamber 111 is located anend of the interior of tube 110 which passes through filtering elements103 (FIG. 6). Referring to FIG. 6, port 121 places chamber 111 in fluidflow relationship with chamber 109. Accordingly, chamber 109 is placedin fluid flow relationship with chamber 108 by the interior of tube 110,chamber 111, and port 121, which are all in fluid flow relationship witheach other. Within conduit 251 is the first outlet of chamber 109 formedby port 124 and the second outlet of chamber 109 formed by port 123.Both port 123 and port 124, constitute passages which lead into chamber109 placing conduit 251 in fluid flow relationship with the chamber 109.A hanging means 244 may be oriented to allow the housing formed by thefirst section 201 and second section 202 to be gravity hung. In thehanging position, the second outlet formed by port 123 is located abovefirst outlet formed by port 124 for improved operation of the filtrationdevice.

Referring still to FIG. 6, the inlet section 201 is engaged with outletsection 202 to form a housing. The edges of the filtration elements 103are located between the inlet section 201 and outlet section 202. Seal120 is used to seal the inlet section 201 to the outlet section 202.Inlet port 122 leads to chamber 108 which is in fluid flow relationshipwith tube 110. Hydrophobic filter 104 is located at one end of tube 110to prevent liquid to be filtered, such as blood, from passingtherethrough. A seal 105 seals the hydrophobic filter to the tube 110.The washer 118 is placed around tube 110 so that filtration elements 103are located between the washer 118 and a lip 299. Hydrophilic filter 106is preferably located over port 123 to prevent air from within thechamber 109 from flowing through the port 123 when hydrophilic filter106 is wet. The hydrophilic filter may be recessed within a well 207.Preferably, a heat seal is used to seal the hydrophilic filter to theoutlet section 202. Port 123 is in fluid flow relationship with conduit251. A nipple 260 may be formed around port 123 for allowing filteredfluid, such as blood, from flowing therethrough into a collection tube117 and eventually into a collection bag 221.

Operation of the embodiment depicted in FIGS. 5-9 occurs similar to theembodiment of the device depicted in FIGS. 1-4. However, in lieu ofexternal tube 116, conduit 251 transports filtered blood from the outlet124 to the fluid collecting tube 117. Also, chamber 108 and chamber 109are reduced in volume to minimize the volume of air purged intoreceiving blood bag 221. Using such a configuration, first section 101may require a recessed area 260 to allow tube 110 to protrude intochamber 108.

FIG. 7 depicts a sectional view of the aforementioned embodiment of thefiltration device 229. On the inside surface of second section 202 aplurality of ribs 242 are located. The ribs 242 serve to stabilize theposition of filtration elements 103 while allowing liquid such as bloodto be filtered to flow through chamber 109. The ribs prevent thepressure exerted within chamber 108 from deforming the filtrationelements 103. FIG. 8 depicts the inside surface of first section 201.Recess 260 contains a ridge 261 located on one or more edges thereof andextending from the inside surface 230 of the first section. As shown inFIG. 6, ridge 261 contacts washer 118 to maintain a force against theportion of filtration elements 103 between the washer 118 and lip 299.

Referring to FIG. 9, the fluid filtration device when used to filterblood may be used by placing a blood supply bag 220 in fluid flowrelationship with an in-line vent filter 15. Blood flowing through thevent filter is carried by a conduit 13 to filtration device 229 viainlet nipple 113. A collection tube 117 is connected to an outlet nipple260, at one end, and at the other end to a blood collecting bag 221. Thefiltration of blood occurs without the need for manually opening andclosing vents or for moving the blood collecting bag to differentheights relative to the blood supply bag or housing 229.

FIG. 10 is an exploded view of the lower part of the filtration device229 depicted in FIG. 6 for the purposes of depicting sealing techniquesuseable in connection with the present invention. The fluid filtrationdevice 229 contains four filtration elements 103. However, more or lessthan four filtration elements 103 may be used depending on theapplication. Each filtration element 103 may provide a logarithmicreduction of leukocytes from the blood that passes through that layer.For example, if unfiltered blood initially contains 1,000 leukocytes/ml,it will contain 100 leukocytes/ml after passing through one filtrationelement 103. Hence four leukocyte filtration elements 103 should givefour orders of logarithmic reduction of leukocytes and/or other bloodcomponents. FIG. 10 illustrates the blood flow path through fourfiltration elements 103. Blood may bypass filtration through each of theelements. For example, blood flow may start in chamber 108 and followsthe shortest path from chamber 108 through the first filtration elementinto gap 284 between tube 110 and the edge of the filtration elements103 and through the last filtration elements 103 into chamber 109.

If the distance travelled by blood, which flows through the filtrationelements 103 and gap 284 is less than the thickness of all of thefiltration elements 103, then blood may bypass some of the elements andmay not be adequately filtered. One solution to the problem is toincrease the diameter of washer 218 and to increase the width of ring250. This will increase the length that blood bypassing the intermediatelayers of filtration elements must travel. However, since tube 110 andring 299 should be located near the bottom of the device, there is alimit to their diameters. Moreover, increasing the diameter of washer118 increases the possibility for wrinkles to form in elements 103causing blood to flow therethrough and avoid complete filtration.

A preferred solution to the above mentioned bypass problem isillustrated in FIG. 11. In FIG. 11, flanged washers 285, 286, 287 and288 independently seal each layer of the leukocyte removing elements 103around tube 110. Each flanged washer should be sized to contact eitherthe washer stacked thereupon, surface 255, or ridge 261 depending uponits position. Also, preferably flanged washers 285, 286, 287, and 288,are press fit around tube 110. However, other reliable sealingtechniques could be used to seal the flanged washers to tube 254. Also,instead of sealing each of the flanged washers to tube 110, eachinterior flanged washer could be sealed to the adjoining washers.Moreover, the flanged washer contacting ridge 261 may be sealed theretoand/or the flange washer contacting surface 255 may be sealed to surface255. Also, it may be possible to use a number of flanged washers whichare less than the number of filtration elements. If a press fit is usedbetween the flanged washers and tube 254, then the flanged washers andtube 254 may be made of dissimilar materials which are preferablyradiation sterilizable. The flange of the flanged washers should be madeas thin as practical so as to minimize wrinkling of the filtrationelements 103. Ridge 261 of inlet half 201 prevents the flanged washersfrom rising on tube 254 once inlet half 201 is sealed to outlet half202.

FIG. 12 depicts the lower portion of the embodiment of the filtrationdevice 229 depicted in FIG. 11 using an alternative means for sealingthe edges of filtration elements 103. Flanged rings 271, 272, 273, 274are placed over the edges of each filtration element 103. Each flangedring may be sealed to the second section 202, or each flanged ring maybe sealed to its adjacent flanged ring and the lower flanged ring 274sealed to second section 202. Also, each or some of the flanged rings271, 272, 273, 274 may be press fit against side wall 245 of secondsection 202. Each flanged ring should extend throughout the outer edgeof the filtration elements. Also, it may be possible to use a number offlanged rings which is less than the number of filtration elements.

FIG. 13 depicts an alternative technique for sealing the edges offiltration elements 103. Using this technique, the edge 276 of thebottom filtration element is bonded to second section 202, preferably bya heat seal which extends around the entire periphery of the filtrationelement 103. The heat seal, however, will compress the fibers at theedges 276, 277, 278, 279, of the filtration element which willeffectively reduce the filtration capability of the elements at theinterface between the compressed and noncompressed region. To preventreduced filtration capability, layers of polyethylene film 98 may beplaced between each layer of the filtration elements 103 prior tosealing the edges of each layer 276, 277, 278, 279 to one another. Thepolyethylene film layers 98 prevent blood from filtering through theinterface regions affected by the heat sealing. Other thermoplasticfilms may be used in lieu of a polyethylene film 98. However, the filmlayers should extend around the entire periphery of filtration elements103. Also, the edge 276 of the lower filtration element may be sealed tosecond section 202 and the other edges 277, 278, 279 of the filtrationelements may be sealed to one another. However, other patterns andtechniques for sealing the edges 276, 277, 278, 279 to one another or tothe second section 202 may be used.

FIG. 14 illustrates yet another embodiment of the invention. Thisfiltration device does not contain a second outlet from the secondchamber 109 or a means for placing the first outlet 124 in fluid flowrelationship to a second outlet. Tubing 168 looping around the back offiltration device 129 acts a means for placing the first chamber 108 influid flow relationship with the second chamber. Assuming the filtrationof blood within the device 129, as discussed supra, a sterile connectionwould be made between tubing 14 and feed blood bag 20. The systemcomponents would then be suspended as depicted in FIG. 14. Blood wouldflow from tubing 13 through port 122 into chamber 108 of inlet half 101.Chamber 108 will fill from the bottom up until chamber 108 is full. Aswith previous embodiments tubing socket 113 and port 122 can be locatedanywhere on inlet half 101. Filter 104 is a hydrophobic filter whichprevents blood from flowing therethrough. As chamber 108 begins to fill,filtration elements 103 will begin to wet from the bottom up. As chamber108 fills, the air in chamber 108 will vent through the non wet portionsof filtration elements 103 into chamber 109. This air will exit fromchamber 109 into receiving blood bag 21 through port 124 and tubing 117.As filtration elements 103 wet, the air that was in these filtrationelements will also vent into chamber 109 and then into receiving bloodbag 21 through port 124 and tubing 117. Blood will begin to flow throughfiltration elements 103 from the bottom up. At this point both blood andair will be passing from filtration elements 103-into chamber 109 ofoutlet section 102 and a mixed stream of blood and air will pass throughport 124 and tubing 117 into receiving blood bag 21. This process willcontinue until filtration elements 103 are completely wet with blood.The blood level in chamber 109 will then rise to a level just above thelevel of tubing 117 as depicted in FIG. 14. At this point tubing 117will be full of blood (i.e., no air) and air will cease to flow intoreceiving blood bag 21.

When feed blood bag 20 is empty air will pass from ports 4 throughhydrophobic filter 3 of the vent 15. Vent filter 15, tubing 13 andchamber 108 of inlet section 101 will drain through filtration elements103 into chamber 109 of outlet section 102. Chamber 108 will drain fromthe top down. Once the blood level in chamber 108 falls below the nonsealed portion of hydrophobic filter 104 air will begin to pass fromchamber 108 through port 194, tubing 168 and port 169 into chamber 109.This air flow from chamber 108 to chamber 109 will bring chamber 109 toatmospheric pressure thus draining chamber 109 and tubing 117 intoreceiving blood bag 21. To ensure that chamber 108 drains completelyhydrophobic filter 104 should be placed at the bottom of chamber 108 andhydrophobic filter 104, should be of small enough pore size to give thenecessary delay (i.e., to allow chamber 108 to finish draining beforeenough air passes through hydrophobic filter 104 into chamber 109 andcauses chamber 109 to drain). If hydrophobic filter 104, tubing socket167 and port 194 are located at a higher location on inlet half 101filtration device 129 will still filter in the same manner, but chamber108 will not completely drain at the end of the filtration process.

Although the invention has been depicted in connection with theembodiments disclosed herein, it will be apparent to one of ordinaryskill in the art that the invention may be performed using variousmodifications and substitutions to the embodiments depicted herein. Anysuch modifications or substitutions are intended to be within the scopeof the invention as defined by the following claims.

What is claimed is:
 1. A method of processing biological liquid from anenclosed flexible supply bag through a filtration media of a processingsystem comprising:flowing biological liquid into an inlet and out of anoutlet of said system; automatically restricting the flow of biologicalliquid within said system downstream of a port, located adjacent orupstream of said filtration media, said port covered with a hydrophobicfilter material to allow biological liquid to back up above the level ofsaid port within said system during filtration, said port leadingoutside of said system and being located downstream of said inlet andupstream of said filtration media; automatically preventing gas fromentering into said processing system through said port duringfiltration, without closing a flow restriction clamp after biologicalliquid flows downstream of said port, by maintaining the level ofbiological liquid above the port until the flow of biological liquidfrom said flexible supply bag ceases; and automatically allowing gas toenter the system through said port when the flow of liquid ceasesthereby automatically draining biological liquid within said system intoa receiving container.
 2. The method of claim 1 wherein the flow ofbiological liquid is restricted by a narrow cross-sectional area withinsaid processing system.
 3. The method of claim 2 wherein said biologicalliquid is blood or a blood product.
 4. The method of claim 3 whereinsaid filtration media comprises a leukocyte filter media.
 5. The methodof claim 4 wherein the biological liquid flows into a receiving bag. 6.The method of claim 5 wherein said receiving bag is located at a heightbelow said leukocyte filter media and below said port.
 7. The method ofclaim 6 wherein said port is located at a height greater than saidleukocyte filter media.
 8. A method of filtering leukocytes from bloodor a blood product in a sterile system comprising:flowing blood or bloodproduct into an inlet and out of an outlet into a receiving container ofsaid system; automatically restricting the flow of blood or bloodproduct downstream of a port and upstream of said receiving containerduring filtration, without closing a flow restriction clamp after bloodor blood product flows downstream of said port, to prevent external gasfrom entering into the system through said port and mixing with theblood or blood product, said port leading outside of said system andbeing covered with a hydrophobic filter media, said port being locateddownstream of said inlet and upstream or adjacent a leukocyte filter;flowing blood or blood product through the leukocyte filter, saidleukocyte filter being located downstream of said port and upstream ofsaid outlet; automatically allowing gas to enter the system through theport when the flow of blood or blood product ceases to therebyautomatically drain blood or blood product remaining within the systeminto said receiving container.
 9. The method of claim 8 wherein the portis positioned upstream of said leukocyte filter.
 10. The method of claim9 wherein the port is located between a blood supply bag and theleukocyte filter.
 11. The method of claim 9 wherein the blood or bloodproduct is drained into a collection bag.
 12. A method of processing abiological liquid comprising:flowing biological liquid through an inletof a processing system, said processing system having a port thereincovered with a hydrophobic filter media, said port leading to outside ofsaid system and adapted to keep the system sterile; automaticallyrestricting the flow of liquid downstream of the port and upstream of anoutlet of said processing system while flowing said liquid through thesystem and through a filtration media, without closing a flowrestriction clamp after biological liquid flows downstream of said port,so that the pressure head of the fluid in the system at the level ofsaid port is greater than atmospheric pressure, said port being locateddownstream of said inlet and upstream of said outlet; and automaticallyallowing gas to enter the port when the pressure of the fluid in thesystem at the level of the port becomes less than atmospheric pressureto drain biological liquid remaining within the system into a saidreceiving container.
 13. A method of claim 12 wherein the flow ofbiological liquid is restricted by a narrow cross-sectional area withinsaid processing system.
 14. The method of claim 13 wherein saidbiological liquid is blood or a blood product.
 15. The method of claim14 further comprising filtering leukocytes from the blood or bloodproduct flowing within the system.
 16. The method of claim 15 whereinthe biological blood or blood product flows into a receiving bag. 17.The method of claim 16 wherein said port is located upstream of saidfiltration media.
 18. The method of claim 17 wherein said receiving bagis located at a height below said filtration media and below said port.19. A biological liquid filtration system including a receivingcontainer, comprising:a filtration media within said system adapted toallow biological liquid to flow therethrough for filtration; aself-contained automatic venting unit, said venting unit comprising aninlet, an outlet and an automatic vent, wherein the outlet is locatedupstream of the filtration media; said automatic vent comprising a portcovered with a hydrophobic filtration media, said automatic vent beinglocated downstream of said inlet and upstream of said filtration media,said automatic vent leading outside of said system and being adapted toautomatically prevent gas from entering said system through said port,without closing a flow restriction clamp after biological liquid flowsdownstream of said port, while the biological liquid flows downstream ofsaid port until the flow of biological liquid ceases and thenautomatically allow gas to enter the system through said port after theflow of biological liquid ceases and then drain biological liquid fromwithin said system into the receiving container.
 20. The system of claim19 further comprising a narrow cross-sectional area within said system,wherein said narrow cross-sectional area is located downstream of saidautomatic vent.
 21. The system of claim 20 wherein said filtration mediacomprises a leukocyte filter media.
 22. The system of claim 21 furthercomprising a receiving bag located downstream of said leukocyte filtermedia.
 23. The system of claim 22 wherein said receiving bag is locatedbelow said port and said leukocyte filter media.
 24. The system of claim23 wherein said port is located at a height greater than said leukocytefilter media.
 25. A method of filtering leukocytes from blood or a bloodproduct within a filtration system comprising:flowing the blood or bloodproduct from a flexible supply bag through an inlet and through aleukocyte filter wherein an outlet is located downstream of said inlet;automatically restricting the flow of blood or blood product downstreamof the inlet and upstream or adjacent to said leukocyte filter duringfiltration, without closing a flow restriction clamp after blood orblood product flows downstream of said port, to prevent external gasfrom entering the system through a port covered by a hydrophobic filtermedia and located downstream of said inlet and upstream of said filterand mixing with the blood or blood product within the system; andautomatically allowing gas to enter the port when the flow of blood orblood product ceases, to thereby allow blood or blood product to drainthrough the leukocyte filter.
 26. A biological liquid filtration systemincluding an inlet and an outlet comprising:a filtration media withinsaid system adapted to allow a biological liquid to flow therethroughfor filtration, said filtration media located upstream of said outlet; avent within said system located upstream of said filtration media anddownstream of said inlet, said vent comprising a port with a hydrophobicfilter thereon; a flow restriction located downstream of said port andadapted to automatically maintain the pressure within the system at saidport above atmospheric pressure to prevent gas from entering said portduring filtration, without closing a flow restriction clams afterbiological liquid flows downstream of said port; and wherein gas enterssaid port automatically when the pressure of said biological liquidwithin the system at the level of said port is less than atmosphericpressure thereby draining biological liquid within said system into areceiving container.
 27. The system of claim 26 wherein the flowrestriction comprises a narrow cross-sectional area within saidfiltration system.
 28. The system of claim 27 wherein said biologicalliquid is blood or a blood product.
 29. The system of claim 28 whereinsaid filtration media comprises a leukocyte filter media.
 30. The systemof claim 29 further comprising a receiving bag downstream of saidleukocyte filter media.
 31. The system of claim 30 further comprisingwherein said port is located upstream of said leukocyte filter media.32. The system of claim 31 wherein said port is located at a heightgreater than said leukocyte filter media.
 33. A method of filteringleukocytes from blood or a blood product comprising:flowing blood or theblood product into an inlet and out of an outlet of a filtration system;flowing the blood or blood product through a leukocyte filter of saidfiltration system; automatically restricting the flow of blood or bloodproduct downstream of said inlet and upstream of said outlet to preventexternal gas from entering the system during filtration, through a portcovered with a hydrophobic filter media and located downstream of saidinlet and upstream of said leukocyte filter without closing a flowrestriction clamp after blood or blood product flows downstream of saidport, and mixing with the blood or blood product within the system;allowing gas to automatically enter the port when the flow of blood orblood product ceases to thereby allow blood or blood product upstream ofthe leukocyte filter to drain.
 34. The method of claim 33 wherein theflow of blood or blood product is restricted by a narrow cross-sectionalarea.
 35. The method of claim 34 wherein the blood or blood productflows into a receiving bag.
 36. The method of claim 34 wherein said portis located at a height greater than said leukocyte filter.
 37. A methodof processing biological liquid through a filtration media of aprocessing system comprising:flowing biological liquid within saidsystem through said filtration media located between an inlet and anoutlet of the processing system; automatically restricting the flow ofsaid biological liquid within said system upstream of said outlet whilefiltration occurs to cause the pressure of biological liquid at a levelof a port covered with a hydrophobic filter media within said system tobe greater than atmospheric pressure, without closing a flow restrictionclamp after biological liquid flows downstream of said port; preventinggas from entering into the processing system through said port locatedupstream of said filtration media and downstream of said inlet bymaintaining the pressure of biological liquid at the level of said portabove atmospheric pressure; and automatically allowing gas to enter thesystem through the port when the pressure of biological liquid withinthe system at the level of the port is less than atmospheric pressurethereby draining biological liquid within said system into a receivingcontainer.
 38. The method of claim 37 wherein the flow of biologicalliquid is restricted by a narrow cross-sectional area within saidprocessing system.
 39. The method of claim 38 wherein said biologicalliquid is blood or a blood product.
 40. The method of claim 39 whereinsaid filtration media comprises a leukocyte filter media.
 41. The methodof claim 40 wherein the biological liquid flows into a receiving bag.42. The method of claim 41 wherein said port is located upstream of saidleukocyte filter media.
 43. The method of claim 42 wherein saidreceiving bag is at a height below than said leukocyte filter media andbelow said port.
 44. A method of processing a biological liquidcomprising:flowing biological liquid through an inlet of a processingsystem, said processing system having a port therein covered with ahydrophobic filter media, said port leading to outside of said systemand adapted to keep the system sterile; automatically restricting theflow of liquid downstream of the port and upstream of an outlet of saidprocessing system while flowing said liquid through the system, withoutclosing a flow restriction clamp after biological liquid flowsdownstream of said port, including a narrow-cross sectional area of thesystem wherein the pressure head of the fluid in the system at the levelof said port is greater than atmospheric pressure, said port beinglocated downstream of said inlet and upstream of said outlet; andautomatically allowing gas to enter the port when the pressure of thefluid in the system at the level of the port becomes less thanatmospheric pressure to drain biological liquid remaining within thesystem into a receiving container.
 45. The method of claim 44 whereinsaid biological liquid is blood or a blood product.
 46. The method ofclaim 45 wherein said system includes a filtration media located betweenthe inlet and the outlet.
 47. The method of claim 46 further comprisingfiltering leukocytes from the blood or blood product flowing within thesystem.
 48. The method of claim 44 wherein said system includes afiltration media located between the inlet and the outlet.
 49. Themethod of claim 48 wherein the port is located upstream of saidfiltration media.
 50. The method of claim 48 wherein the biologicalliquid flows into a receiving bag.
 51. The method of claim 50 whereinsaid receiving bag is located at a height below said filtration mediaand below said port.
 52. A method of processing a biological liquidcomprising:flowing biological liquid through an inlet of a processingsystem, said processing system having a port therein covered with ahydrophobic filter media, said port leading to outside of said systemand adapted to keep the system sterile; automatically restricting theflow of liquid downstream of the port and upstream of an outlet of saidprocessing system to prevent external gas from entering into the systemthrough said port and mixing with the liquid while flowing said liquidthrough the system and through a filtration media, without closing aflow restriction clamp after biological liquid flows downstream of saidport, said port being located downstream of said inlet and upstream ofsaid outlet; and automatically allowing gas to enter the system throughthe port when the flow of liquid ceases and thereby draining biologicalliquid remaining within the system into a receiving container.
 53. Amethod of processing a biological liquid comprising:flowing biologicalliquid through an inlet of a processing system, said processing systemhaving a port therein covered with a hydrophobic filter media, said portleading to outside of said system and adapted to keep the systemsterile; automatically restricting the flow of liquid downstream of theport and upstream of an outlet of said processing system to preventexternal gas from entering into the system through said port and mixingwith the liquid while flowing said liquid through the system and througha narrow-cross section area in the system, without closing a flowrestriction clamp after biological liquid flows downstream of said port,said port being located downstream of said inlet and upstream of saidoutlet; and automatically allowing gas to enter the system through theport when the flow of liquid ceases and thereby draining biologicalliquid remaining within the system into a receiving container.
 54. Themethod of claim 53 wherein said biological liquid is blood or a bloodproduct.
 55. The method of claim 54 wherein said system includes afiltration media located between the inlet and the outlet.
 56. Themethod of claim 55 further comprising filtering leukocytes from theblood or blood product flowing within the system.
 57. The method ofclaim 53 wherein said system includes a filtration media located betweenthe inlet and the outlet.
 58. The method of claim 57 wherein the port islocated upstream of said filtration media.
 59. The method of claim 57wherein the biological liquid flows into a receiving bag.
 60. The methodof claim 59 wherein said receiving bag is located at a height below saidfiltration media and below said port.